Rays and fishing
Rays do not become sexually mature until they are quite old, and they produce few offspring. They are therefore at risk of dying out as a result of fishing.
Trends
On average, the rays of the Dutch Continental Shelf (skate, blond ray, painted ray, roker, spotted ray, cuckoo ray and starry ray) declined sharply in the period 1945-2000 (see left-hand graph). With the exception of the starry ray (see right-hand graph) all the species have declined. The skate, a species of the deeper parts of the North Sea, seems to have disappeared from the Dutch Continental Shelf.
Technical note
The stingray, spotted ray and roker are on the draft Red List of sea fishes.
The left-hand graph shows the Species Group Trend Index (SGTI) for the pooled ray species (skate, blond ray, roker, painted ray, spotted ray, cuckoo ray and starry ray). These are all species that occur or used to occur on the Dutch Continental Shelf more than incidentally. The right-hand graph shows the figures for the starry ray.The data are from old and recent counts by Stichting Anemoon of egg capsules washed up on Dutch beaches. Only data from those counts known to have looked for egg capsules of all rays have been used.
The increase in the starry ray since the 1970s was confirmed by catches per fishing hour made by the International Bottom Trawl Survey (ICES IBTS Database).
References
- Bisseling, C.M. (red.) (2001). Met de natuur in zee; Rapportage project "Ecosysteemdoelen Noordzee", Kennisfase. Expertisecentrum LNV. Wageningen.
- Gmelig Meyling, A.W. en R.H. Bruyne (2001). Een duik in mariene gegevens. Lange termijnveranderingen van populaties van enkele mariene organismen (roggen, weekdieren kreeftachtigen en andere) als gevolg van menselijk handelen. Stichting ANEMOON. Heemstede.
- Heessen, H.J.L., H.C. Welleman, N. Daan, A.C. Smaal en G.J. Piet (2001). Bijdrage RIVO aan Natuurcompendium 2001. Nederlands Instituut voor Visserijonderzoek RIVO. Intern rapport C058/01. IJmuiden.
- Knijn, R.J., T.W.Boon, H.J.L. Heessen en J.R.G. Hislop (1993). Atlas of North Sea fishes. ICES Cooperative Resaerch Report No. 194.
